In searching the net the only solution I've found to separate cast iron pipe is to use a 1/4 inch drill and drill out the lead. After a number of hours -- just on one vertical pipe -- I have still yet to get enough lead and okum out to separate the pipe from the hub.

When cast iron was commonly used, I'm sure electricity was Not always available to try and drill lead nor can I imagine someone spending 8 hours or more to separate two pipes from each other. Other than cutting the pipe -- which would not leave the hub available --
anyone have a solution?

First, thanks for all the feedback.
I guess my original post was not clearly stated.

I want to remove the pipe from the hub - Not - cut it off above the hub.
The reason for this is that once the vertical riser is removed the cast will be plugged at the hub, then a concrete slab poured on top of where the hub is located. To get the slab depth needed the vertical needs to be removed not cut. Breaking the hub with a sludge will also - Not - work as it goes though a concrete block wall and any extra force used may destroy the block which will create another and bigger problem.

isola96 -- one option maybe to cut off vertical above hub and then try and saw cast from inside out. Tried one metal cutting blade and teeth failed after less than a minute. Have heard Lennox blades listed for cast do -Not- work either.
Will check on tungsten.

Did you ever get any worth while responses from your post on separating cast iron pipe? I have to do the same thing you did, and was planning to use the drilling technique -- now I have my doubts whether I will have any better luck than you did.